Semiconductor light emitting apparatus and its manufacturing method

ABSTRACT

A semiconductor light emitting apparatus comprises: a semiconductor light emitting device; resin that seals the semiconductor light emitting device; and antireflective coating provided on a surface of the resin. The antireflective coating is made of material having an intermediate refractive index between the refractive index of the resin and the refractive index of air.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2004-058197, filed on Mar. 2,2004; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a semiconductor light emitting apparatus andits manufacturing method, and more particularly, to a so-calledmold-type semiconductor light emitting apparatus having a light emittingdevice sealed with resin, the semiconductor light emitting apparatushaving improved extraction efficiency of light from the mold resin tothe air and its manufacturing method.

One of the typical semiconductor light emitting apparatuses is asemiconductor light emitting apparatus having a semiconductor lightemitting device such as LED (light emitting diode) or LD (laser diode)sealed with mold resin. Many of the compound semiconductors constitutingsuch a semiconductor light emitting device have refractive index in thelight emission wavelength region as high as about 3.2 to 3.7. On theother hand, the mold resin has refractive index as low as about 1.5. Forthis reason, since light emitted from the light emitting area isincident from the compound semiconductor layer having high refractiveindex on the mold resin having low refractive index, it is totallyreflected at the interface with the mold resin for incident anglesgreater than the critical angle. This causes a problem of decreasedlight extraction efficiency. In this respect, total reflection can besuppressed by roughening the surface of the compound semiconductor(e.g., Japanese Laid-Open Patent Application 2003-174191).

As described above, optical transmittance from the semiconductor lightemitting device to the mold resin can be improved.

However, with respect to light extraction from mold resin to the air,the transmittance is restricted by the difference between theirrefractive indices. Thus there is a problem that the light extractionefficiency is still low.

SUMMARY OF THE INVENTION

According to an aspect of the invention, there is provided asemiconductor light emitting apparatus comprising: a semiconductor lightemitting device; resin that seals the semiconductor light emittingdevice; and antireflective coating provided on a surface of the resin,the antireflective coating being made of material having an intermediaterefractive index between the refractive index of the resin and therefractive index of air.

According to another aspect of the invention, there is provided asemiconductor light emitting apparatus comprising: a semiconductor lightemitting device; and resin that seals the semiconductor light emittingdevice, wherein at least a portion of the surface of the resin isprovided with asperities having an average pitch less than ½ of awavelength of light emitted through the resin.

According to another aspect of the invention, there is provided a methodof manufacturing a semiconductor light emitting apparatus comprising:mounting a semiconductor light emitting device on a mounting member;molding the semiconductor light emitting device by a resin havingasperities on at least a part of a surface thereof, the asperitieshaving an average pitch less than ½ of a wavelength of light emittedthrough the resin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing a semiconductor lightemitting apparatus according to a first embodiment of the invention;

FIG. 2 is a graphical diagram illustrating the relationship between thefilm thickness of antireflective coating 6 and the reflectance;

FIG. 3 is a schematic cross-sectional view showing a semiconductor lightemitting apparatus according to a second embodiment of the invention;

FIG. 4 is a conceptual diagram for illustrating the function ofasperities 7R;

FIGS. 5 to 7 are conceptual diagrams for illustrating the change ofwidths a and b of the periodic structure;

FIG. 8 is a schematic diagram for illustrating the distribution ofeffective refractive index for light L transmitted through theasperities 7R;

FIG. 9 is a schematic diagram illustrating the distribution ofrefractive index in oblique asperities 7R;

FIGS. 10 and 11 are schematic diagrams showing another specific exampleof asperities 7R that can be provided in the second embodiment;

FIG. 12 is a schematic diagram showing a semiconductor light emittingapparatus in which projections or depressions of irregular shape areirregularly arranged;

FIG. 13 is a schematic diagram showing a semiconductor light emittingapparatus having asperities 7R in which projections having a generallyperpendicular side surface are periodically or irregularly arranged;

FIG. 14 is a schematic diagram showing the cross section of a mold thatcan be used for manufacturing a semiconductor light emitting apparatusof the second embodiment;

FIG. 15 is a conceptual diagram for illustrating the nanoimprintingmethod;

FIG. 16 is a process cross-sectional view showing part of the processusing block copolymer;

FIG. 17 is a schematic view showing an example of variation of thesemiconductor light emitting apparatus;

FIG. 18 is a schematic cross-sectional view showing another example ofvariation of the semiconductor light emitting apparatus; and

FIGS. 19 to 22 are schematic cross-sectional views showing still otherexamples of variation of the semiconductor light emitting apparatus.

DETAILED DESCRIPTION

Embodiments of the invention will now be described with reference to thedrawings.

FIG. 1 is a schematic cross-sectional view showing a semiconductor lightemitting apparatus according to a first embodiment of the invention.

This semiconductor light emitting apparatus comprises a semiconductorlight emitting device 1, a pair of leads 2 and 3, and sealing resin 5.More specifically, the semiconductor light emitting device 1 is mountedon the lead 2 as a mounting member with conductive adhesive or solder(not shown). The semiconductor light emitting device 1 has a structurein which a semiconductor layer 1 b is stacked on a conductive crystalsubstrate 1 a. An n-side electrode 1 c is formed on the rear side of theconductive crystal substrate 1 a. A p-side electrode 1 d is formed onthe upper surface of the semiconductor layer 1 b. The n-side electrode 1c is bonded to the lead 2.

The p-side electrode 1 d of the semiconductor light emitting device 1 iselectrically connected with the lead 3 via a bonding wire 4. Thesemiconductor light emitting device 1 is sealed with mold resin 5 thatserves for protection and lens function.

A p-n junction is formed in the semiconductor layer 1 b of thesemiconductor light emitting device 1. This junction area serves as alight emitting layer, from which light emission is obtained in an upwarddirection, with the upper surface of the n-type layer including thep-side electrode 1 d acting as a light extraction surface. When atransparent substrate is used for the conductive crystal substrate 1 a,light from the light emitting layer can be extracted also from the lowerside.

In this embodiment, the surface of the mold resin 5 is provided withantireflective coating 6 having an intermediate value of refractiveindex between the refractive index of the mold resin 5 and that of air.The antireflective coating 6 has a refractive index and film thicknessselected so as to decrease reflectance for light emitted from thesemiconductor light emitting device 1. The reflectance of theantireflective coating 6 can be made close to zero if the followingrelation is satisfied:2nT=(m−½)λ(m is an integer)where n is the refractive index of the antireflective coating 6, T isits film thickness, and λ is the wavelength of light emitted from thesemiconductor light emitting device 1.

Here, the reflectance obtained when the antireflective coating 6 isprovided can be described as follows.

Assuming that the mold resin 5 and the antireflective coating 6 have nolight absorption, the amplitude reflectance r₁ at the interface betweenthe mold resin 5 and the antireflective coating 6 and the amplitudereflectance r₂ at the interface between the antireflective coating 6 andair can be described by:

$\begin{matrix}{r_{1} = \frac{n_{1} - n_{0}}{n_{1} + n_{0}}} \\{r_{2} = \frac{n_{2} - n_{1}}{n_{2} + n_{1}}}\end{matrix}$where n₀, n₁, and n₂ are the refractive indices of the mold resin 5,antireflective coating 6, and air, respectively.

Here, the overall amplitude reflectance r is given by:

$\begin{matrix}{r = \frac{r_{1} + {r_{2}{\mathbb{e}}^{{\mathbb{i}}\; 2\;\delta}}}{1 + {r_{1}r_{2}{\mathbb{e}}^{{\mathbb{i}}\; 2\;\delta}}}} \\{{\delta = \frac{2\;\pi\; n_{1}T}{\lambda}}\mspace{45mu}}\end{matrix}$

Therefore the reflectance R can be expressed as:

$R = {{r}^{2} = \frac{r_{1}^{2} + r_{2}^{2} + {2r_{1}r_{2}\cos\; 2\delta}}{1 + {r_{1}^{2}r_{2}^{2}} + {2r_{1}r_{2}\cos\; 2\delta}}}$

FIG. 2 is a graphical diagram illustrating the relationship between thefilm thickness of antireflective coating 6 and the reflectance. Morespecifically, this figure shows the dependence of reflectance on thefilm thickness of the antireflective coating 6 that is obtained when thesemiconductor light emitting device 1 has a light emission wavelength of620 nanometers and the antireflective coating 6 is resin thin filmhaving a refractive index of 1.3. Here, it is assumed that therefractive index n₀ of the mold resin 5 is 1.5, and the refractive indexn₂ of air is 1.

As seen from FIG. 2, the reflectance can be significantly decreased whenthe film thickness of the antireflective coating 6 is 120, 355, or 600nanometers. That is, in these cases, the optical transmittance from themold resin 5 to the air is nearly 100%, and thus the light emissionbrightness can be improved.

However, the film thickness T of the antireflective coating 6 is notnecessarily required to be a value that gives the minimal reflectance inFIG. 2. The film thickness T may be selected to generally conform to thefollowing equation:T=(m−½)λ/2n(m is an integer)in the range of the film thickness giving the minimal reflectance plusor minus about 30 nanometers.

The reflectance R can be minimized when the refractive index n₁ of theantireflective coating 6 has a value that satisfies or generallyconforms to the following equation:n ₁=√{square root over (n₀ n ₂)}

The antireflective coating 6 as described above can be formed by variousmethods such as vacuum evaporation, sputtering, CVD (chemical vapordeposition), and coating. In addition to polymer, the material of theantireflective coating 6 may be any of various oxides and fluorides suchas silicon oxide (SiO_(x)) and magnesium fluoride (MgF₂).

Next, the second embodiment of the invention will be described.

FIG. 3 is a schematic cross-sectional view showing a semiconductor lightemitting apparatus according to the second embodiment of the invention.

With respect to this figure, elements similar to those described withreference to FIG. 1 are marked with the same numerals and are notdescribed in detail.

The basic configuration of the semiconductor light emitting apparatus ofthis embodiment is similar to that described above with reference to thefirst embodiment. The semiconductor light emitting device 1 is sealedwith mold resin 7 that serves for protection and lens function. In thisembodiment, fine asperities 7R are formed on the surface of the moldresin 7. The pitch P of the asperities 7R is set to be less than ½ ofthe light emission wavelength.

Such asperities 7R provided on the surface of the mold resin 7 yield aregion in which the refractive index continuously varies from therefractive index of the mold resin 7 (about 1.5) to that of the air(about 1). This acts as a graded index, enabling the opticaltransmittance from the mold resin 7 to the air to be nearly 100 percent.

FIG. 4 is a conceptual diagram for illustrating the function ofasperities 7R.

More specifically, in this embodiment, as shown in FIG. 4A, light Lemitted from the semiconductor light emitting device 1 passes throughthe sealing resin 7, and is emitted into the air through the surfaceregion in which the asperities 7R are formed. At this time, in theasperities 7R, the resin 7 (corresponding to projections of the resin 7)alternates with the air (corresponding to depressions of the resin 7).

FIG. 4B is a conceptual diagram showing a periodic structure in whichthe resin 7 alternates with the air in this manner. More specifically,light L travels in a generally perpendicular direction relative to therepeat direction of the repetitive structure in which the resin 7adjacently alternates with the air. In this case, assuming that theresin 7 (projections) has a refractive index of n₁ and a width of a, andthe air (depressions) has a refractive index of n₂ and a width of b, therefractive index can be approximated by:

$\begin{matrix}{n = \sqrt{\frac{{a\; n_{1}^{2}} + {b\; n_{2}^{2}}}{a + b}}} & (1)\end{matrix}$when the widths a and b are sufficiently small as compared to thewavelength λ.

As seen from Equation (1), the average refractive index in theasperities 7R has an intermediate value between the refractive index n₁of the resin 7 and the refractive index n₂ of the air.

In order for the approximation of Equation (1) to hold, the widths a andb of the respective layers must be smaller than the wavelength λ so asto satisfy the following condition (S. M. Rytov, Sov. Phys. JETP 2(1956) 466):

$\begin{matrix}\begin{matrix}{{{\tan\left( {\frac{n_{1}a}{\lambda}\pi} \right)} \cong {\frac{n_{1}a}{\lambda}\pi}},} \\{{\tan\left( {\frac{n_{2}b}{\lambda}\pi} \right)} \cong {\frac{n_{2}b}{\lambda}\pi}}\end{matrix} & (2)\end{matrix}$

Here, assuming that the refractive index n₁ of the resin 7 (projections)is n₁=1.5 and the refractive index n₂ of the air (depressions) is n₂=1,and that the pitch P=a+b, at least the condition of P/λ being less than½ is required.

In this embodiment, the widths a and b of the periodic structure shownin FIG. 4B are sequentially varied by forming the asperities 7R in acurved or oblique configuration.

FIGS. 5 to 7 are conceptual diagrams for illustrating the variation ofwidths a and b of the periodic structure.

More specifically, in a periodic structure along a cut line X near thebottom of the asperities 7R as shown in FIG. 5A, the width a of theresin 7 (projections) is larger and the width b of the air (depressions)is smaller as shown in FIG. 5B. As seen from Equation (1), the averagerefractive index n in this portion has a value close to the refractiveindex n₁ of the resin 7.

On the other hand, in a periodic structure along a cut line X abouthalfway through the asperities 7R as shown in FIG. 6A, the width a ofthe resin 7 (projections) is close to the width b of the air(depressions) as shown in FIG. 6B. That is, as seen from Equation (1),the average refractive index n in this portion has an intermediate valuebetween the refractive index n₁ of the resin 7 and the refractive indexn₂ of the air.

Furthermore, in a periodic structure along a cut line X near the tip ofthe asperities 7R as shown in FIG. 7A, the width b of the air(depressions) is larger than the width a of the resin 7 (projections) asshown in FIG. 7B. That is, as seen from Equation (1), the averagerefractive index n in this portion has a value closer to the refractiveindex n₂ of the air rather than the refractive index n₁ of the resin 7.

FIG. 8 is a schematic diagram for illustrating the distribution ofeffective refractive index for light L transmitted through suchasperities 7R.

More specifically, when light L passes through the asperities 7R asshown in FIG. 8A, the effective refractive index n continuously variesfrom the refractive index n₁ of the resin 7 to the refractive index n₂of the air in the asperities 7R as shown in FIG. 8B. That is, a “gradedindex” is formed here. In such a graded index structure havingcontinuously varying refractive index, the reflectance of light can besignificantly reduced.

To achieve a graded index structure, the asperities 7R may be formed inan oblique configuration rather than the curved configuration.

FIG. 9 is a schematic diagram illustrating the distribution ofrefractive index in oblique asperities 7R.

As shown in FIG. 9A, when asperities 7R are formed to have a crosssection of generally oblique and linear configuration, the effectiverefractive index n also continuously varies from the refractive index n₁of the resin 7 to the refractive index n₂ of the air in the asperities7R. Therefore also in this case, a graded index structure is formed, andthe reflectance for light L can be significantly reduced.

FIG. 10 is a schematic diagram showing another specific example ofasperities 7R that can be provided in this embodiment. In this specificexample, asperities 7R are formed in which projections protruding fromthe resin 7 toward the air are densely provided. With such asperities7R, as shown in FIG. 10B, it is also possible to form a graded indexthat continuously varies from the refractive index n₁ of the resin 7 atthe surface of the resin 7 to the refractive index n₂ of the air. As aresult, the reflectance for light L can be significantly reduced.

FIG. 11 is a schematic diagram showing another specific example ofasperities 7R that can be provided in this embodiment. In this specificexample, asperities 7R are formed in which convex dimples formed fromthe side of the air toward the resin 7 are densely provided. With suchasperities 7R, as shown in FIG. 11B, it is also possible to form agraded index.

FIGS. 3 to 11 illustrate asperities 7R in which projections ordepressions of fixed shape are periodically arranged. However, theinvention is not limited thereto. That is, as shown in FIG. 12, theasperities 7R may be such that projections or depressions of irregularshape are irregularly arranged. The depressions or projections may beirregularly formed in a curved configuration, in addition to thoseillustrated in FIG. 12. With such irregular asperities 7R, the averagerefractive index also varies almost continuously from the resin 7 towardthe air, and thus a graded index can be formed.

It should be noted that such irregular asperities 7R may be provided sothat their average pitch is less than ½ of the light emissionwavelength.

As illustrated in FIG. 13, it is also possible to provide asperities 7Rin which projections having generally perpendicular side surfaces arearranged periodically or irregularly. In this case, the distribution ofrefractive index near the asperities 7R is as shown in FIG. 13B. Morespecifically, in the asperities 7R, the average refractive index givenby Equation (1) has a nearly uniform distribution. That is, anintermediate refractive index between the refractive index of the resin7 and that of the air is obtained. In this case, the refractive index isnot continuously varied, but produces a jump in the distribution.However, an effect of reducing reflectance can be obtained byalleviating the difference of refractive index between the resin 7 andthe air.

Next, a method of manufacturing a semiconductor light emitting apparatusof this embodiment will be described.

FIG. 14 is a schematic diagram showing the cross section of a mold thatcan be used for manufacturing a semiconductor light emitting apparatusof this embodiment. More specifically, the mold illustrated in thisfigure is used for molding resin 7 of the semiconductor light emittingapparatus. Molding of resin 7 can be carried out by various methods suchas dipping and injection molding. For example, in the dipping method,fluid resin is poured into a mold 300, and the resin may be cured whilethe tip of leads 2 and 3 with the semiconductor light emitting device 1mounted thereon is dipped in the resin.

In this embodiment, the inner surface of the mold 300 is provided withtransfer asperities 300R in advance. This configuration can betransferred to the surface of the resin 7 to form the asperities 7R. Itshould be noted that the transfer asperities 300R illustrated in FIG. 14correspond to those forming the asperities 7R shown in FIG. 10. Inaddition, however, the transfer asperities 300R corresponding to variousconfigurations of asperities 7R described above with reference to FIGS.3 to 13 can be provided on the mold 300 to form these asperities 7R.

Another method of providing asperities 7R on the surface of the resin 7may be the nanoimprinting method, for example.

FIG. 15 is a conceptual diagram for illustrating the nanoimprintingmethod. More specifically, a stamper 400 is prepared. On the surface ofthe stamper 400, transfer asperities 400R corresponding to theasperities 7R to be formed on the resin 7 have been formed. The surfaceof the cured resin 7 is pressed onto the stamper 400, and thereby thetransfer asperities 400R of the stamper 400 can be transferred to thesurface of the resin 7 to form the asperities 7R. When a planar stamper400 is used, for example, the resin 7 is rotated as appropriate asindicated by arrow B with being held down in the direction of arrow A.Thus the asperities 7R can be formed evenly on the overall surface ofthe generally bullet-shaped resin 7.

Alternatively, the stamper 400 may have a shape similar to the mold 300shown in FIG. 14. More specifically, a hollow adapted to the shape ofthe resin 7 is prepared like the mold 300 shown in FIG. 14. On its innerwall surface, the transfer asperities 400R shown in FIG. 15 are formed.Cured resin 7 is then inserted into it and pressurized, and thereby theasperities 7R can be formed on the surface of the resin 7.

Another method of providing asperities 7R on the surface of the resin 7may be etching with a mask. After the resin 7 is formed, a fine maskcorresponding to the asperities 7R is formed on the surface of the resin7. The resin 7 is then etched through the mask. In the embodiment of theinvention, as described above with reference to Equations (1) and (2),the pitch of the asperities 7R is as fine as less than half of the lightemission wavelength. In this respect, for example, block copolymer canbe used to form the mask.

FIG. 16 is a process cross-sectional view showing part of the processusing block copolymer.

More specifically, as shown in FIG. 16A, a mask 500 is formed on thesurface of the resin 7. In particular, for example, the surface of theresin 7 is coated with solution of block copolymer composed ofpolystyrene (PS) and polymethyl methacrylate (PMMA) dissolved insolvent. The solvent is then volatilized by prebaking at 110° C. for 90seconds, for example. Subsequently, by annealing in nitrogen atmosphere,PS and PMMA of the block copolymer are phase separated. At this time,the size of the phase-separated PS and PMMA can be set to about 100nanometers, depending on the composition. The condition of annealing forphase separation may be determined as appropriate with respect to thetemperature and time of annealing in view of the softening temperatureof the resin 7.

Subsequently, the phase-separated block copolymer is etched by RIE(reactive ion etching) at a pressure of 1.33 pascals and a power of 100watts under a flow of CF₄ at 30 sccm. The difference of etching ratebetween PS and PMMA results in selective etching of PMMA, forming a mask500 of a fine pattern of PS on the surface of the resin 7 as shown inFIG. 16A.

Subsequently, as shown in FIG. 16B, the resin 7 is etched through themask 500. The method of etching may be either dry etching or wetetching.

Subsequently, as shown in FIG. 16C, the resin 7 provided with asperities7R is obtained by removing the mask 500. For the mask 500 made of PS,ashing with oxygen plasma can be used to remove the mask 500.

As described above, fine asperities 7R can be formed on the surface ofthe resin 7 by forming a fine mask 500 with block copolymer. The blockcopolymer may be made of material composed of an aromatic ringcontaining polymer chain and an acrylic polymer chain.

Alternatively, the block copolymer may be made of material composed ofan aromatic ring containing polymer chain and an aliphatic double bondpolymer chain. Examples of the latter may include polystyrene andpolyisoprene, for example. In this case, after phase separation,polyisoprene can be removed by ozone treatment to form a pattern ofpolystyrene.

The embodiments of the invention have been described with reference tospecific examples. However, the invention is not limited to thesespecific examples. For example, various variations of the semiconductorlight emitting device and the semiconductor light emitting apparatuswith respect to their structure and the like are also encompassed withinthe scope of the invention.

FIG. 17 is a schematic view showing an example of variation of thesemiconductor light emitting apparatus. More specifically, thesemiconductor light emitting device 1 is formed on an insulatingsubstrate 1 e. In this case, part of an n-type semiconductor layer 1 fformed on the substrate 1 e may be exposed to provide an n-sideelectrode 1 c, which may be connected to the lead 2 using a wire 4A.Such a semiconductor light emitting device may be, for example, aGaN-based semiconductor light emitting device formed on a sapphiresubstrate.

FIG. 18 is a schematic cross-sectional view showing another example ofvariation of the semiconductor light emitting apparatus. Thesemiconductor light emitting apparatus of this example is a resin-sealedsemiconductor light emitting apparatus called of “bullet-shaped” type,similar to those shown in FIGS. 1 and 3.

A cup portion 2C is provided on top of the lead 2. The semiconductorlight emitting device 1 is mounted on the bottom surface of the cupportion 2C with adhesive or the like. It is connected to another lead 3using a wire 4. The inner wall surface of the cup portion 2C constitutesa light reflecting surface 2R, which reflects light emitted from thesemiconductor light emitting device 1. Thus the light can be extractedin an upward direction.

The periphery of the cup portion 2C is sealed with translucent resin 7.The light extraction surface 7E of the resin 7 forms a condensingsurface, which can condense light emitted from the semiconductor lightemitting device 1 as appropriate to achieve a predetermined lightdistribution.

FIG. 19 is a schematic cross-sectional view showing still anotherexample of variation of the semiconductor light emitting apparatus. Morespecifically, in this example, the resin 7 sealing the semiconductorlight emitting device 1 has rotational symmetry about its optical axis7C. It is shaped as set back and converged toward the semiconductorlight emitting device 1 at the center. The resin 7 of such shape resultsin light distribution characteristics where light is scattered at wideangles.

FIG. 20 is a schematic cross-sectional view showing still anotherexample of variation of the semiconductor light emitting apparatus. Morespecifically, this example is called of the “surface mounted” type. Thesemiconductor light emitting device 1 is mounted on a lead 2, andconnected to another lead 3 using a wire 4. These leads 2 and 3 aremolded in first resin 9. The semiconductor light emitting device 1 issealed with second translucent resin 7. The first resin 9 has anenhanced light reflectivity by dispersing fine particles of titaniumoxide, for example. Its inner wall surface 9R acts as a light reflectingsurface to guide light emitted from the semiconductor light emittingdevice 1 to the outside.

FIG. 21 is a schematic cross-sectional view showing still anotherexample of variation of the semiconductor light emitting apparatus. Morespecifically, this example is also called of the “surface mounted” type.The semiconductor light emitting device 1 is mounted on a lead 2, andconnected to another lead 3 using a wire 4. The tips of these leads 2and 3, together with the semiconductor light emitting device 1, aremolded in translucent resin 7.

FIG. 22 is a schematic cross-sectional view showing still anotherexample of variation of the semiconductor light emitting apparatus. Inthis example, a structure similar to that described above with referenceto FIG. 18 is used. In addition, the semiconductor light emitting device1 is covered with fluorescent material 20. The fluorescent material 20serves to absorb light emitted from the semiconductor light emittingdevice 1 and convert its wavelength. For example, ultraviolet or blueprimary light is emitted from the semiconductor light emitting device 1.The fluorescent material 20 absorbs this primary light and emitssecondary light having different wavelengths such as red and green. Forexample, three kinds of fluorescent materials may be mixed, and thefluorescent materials 20 may absorb ultraviolet radiation emitted fromthe semiconductor light emitting device 1 to emit white light composedof blue, green, and red light.

The fluorescent material 20 may be applied to the surface of thesemiconductor light emitting device 1, or may be contained in the resin7.

In any semiconductor light emitting apparatus shown in FIGS. 17 to 22,the antireflective coating 6 as described above with reference to FIG. 1or the asperities 7R as described above with reference to FIGS. 3 to 16may be provided, and thereby light emitted from the semiconductor lightemitting device 1 can be emitted from the resin 7 to the air whilereducing reflection. As a result, light extraction efficiency can besignificantly improved, and a semiconductor light emitting apparatuswith high brightness can be offered.

On the other hand, any details of the layered structure constituting thesemiconductor light emitting device 1 modified as appropriate by thoseskilled in the art are also encompassed within the scope of theinvention, as long as they comprise the feature of the invention. Forexample, the active layer may be made of various materials includingInGaAlP-based material, Ga_(x)In_(1-x)As_(y)N_(1-y)-based (0≦x≦1, 0≦y<1)material, AlGaAs-based material, and InGaAsP-based material. Similarly,the cladding layers and optical guide layer may also be made of variousmaterials.

Any shape and size of the semiconductor light emitting device 1 modifiedas appropriate by those skilled in the art are also encompassed withinthe scope of the invention, as long as they comprise the feature of theinvention. The so-called “flip-chip” type semiconductor light emittingdevice may also be used.

Any other semiconductor light emitting apparatuses that can be modifiedand implemented as appropriate by those skilled in the art on the basisof the semiconductor light emitting apparatuses described above as theembodiments of the invention also belong to the scope of the invention.

While the present invention has been disclosed in terms of theembodiment in order to facilitate better understanding thereof, itshould be appreciated that the invention can be embodied in various wayswithout departing from the principle of the invention. Therefore, theinvention should be understood to include all possible embodiments andmodification to the shown embodiments which can be embodied withoutdeparting from the principle of the invention as set forth in theappended claims.

1. A semiconductor light emitting apparatus comprising: a semiconductorlight emitting device; a resin that seals the semiconductor lightemitting device; and antireflective coating provided on a surface of theresin, the antireflective coating being made of material having anintermediate refractive index between the refractive index of the resinand the refractive index of air, wherein the antireflective coating isprovided with a film thickness that generally conforms to an equation:T=(m−½)λ/2n where λ is a wavelength of light, m is an integer, n is therefractive index of the antireflective coating, and T is the filmthickness.
 2. The semiconductor light emitting apparatus as claimed inclaim 1, wherein the antireflective coating has a thickness in a rangeof plus or minus 30 nanometers from the film thickness that conforms tothe equation.
 3. The semiconductor light emitting apparatus as claimedin claim 1, wherein the refractive index n of the antireflective coatinggenerally conforms to an equation:n=√{square root over (n₀ n ₂)} where n₀ is the refractive index of theair, and n₂ is the refractive index of the resin.
 4. The semiconductorlight emitting apparatus as claimed in claim 1, wherein theantireflective coating is made from a material selected from a groupconsisting of polymers, oxides and fluorides.
 5. The semiconductor lightemitting apparatus as claimed in claim 1, wherein the resin has a lightextraction surface that controls a distribution of a light emitted fromthe semiconductor light emitting device.
 6. The semiconductor lightemitting apparatus as claimed in claim 1, further comprising afluorescent material that absorbs a light emitted from the semiconductorlight emitting device and converts its wavelength.